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Author Topic: Antenna Help  (Read 1113 times)
N3UMH
Member

Posts: 153




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« Reply #15 on: April 21, 2006, 01:52:19 PM »

I hadn't though VHF LOS propagation through at all carefully until today.

At 10 miles on flat earth with 15' high antennas, your LOS path is grazing the radio horizon, and so has to go through or around every house, car, dog, hill and tree along that path.  Also, due to ground reflections, you're not going to have much power down at very low elevation angles.

It's not the distance per se that requires gain antennas and/or high power (the free space path loss would be minimal), but the loss from propagating through or diffracting around a bunch of clutter and also the ground reflection losses from having your antenna mounted above real ground.

I'm with you now, AA4PB... put the antennas 15 feet above the roof.

I will think about cheapie 5/8th over 5/8th waves more...

73...

N3OX
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WB2WIK
Member

Posts: 20611




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« Reply #16 on: April 21, 2006, 03:21:45 PM »

If you can listen to the MURS channels with a big antenna up 50+ feet and hear "nothing," either you're really in the boonies or maybe the receiver doesn't work!

Probably the "boonies" situation, I'd guess.

Where I am in Los Angeles, all five channels are occupied 24/7 as far as I can tell.  Of course, FRS is like that, too, even listening with the little rubber duckie they give you on the FRS radios.

I wanted to use a pair of FRS hand helds to talk to my kids down below when I was up on the tower a couple of months ago (they're not licensed, couldn't use ham gear) and as soon as I got up there, every single channel was so occupied I could hardly hear my kids a hundred feet away.

Makes me wonder if people are really all using hand helds with attached antennas....

WB2WIK/6
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N3NYC
Member

Posts: 63




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« Reply #17 on: April 21, 2006, 03:28:26 PM »

If the way the stations are laid out permits, a small (3 or 4 element) Yagi might work.  Plans for Yagis made out of #8 copper wire and 1x2 lumber can be found in back-issues of CQ-VHF magazine from 1998 and '99.  They're cheap, easy-to-build, tolerant of imprecision in assembly, and have good performance.  I've built a couple, and they work just fine as-built-- no tweaking needed.  And a design for 146 MHz is easily scaled for 152 MHz service.

Good luck and 73,

Hale
November Three New York Central
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KI4CYB
Member

Posts: 47




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« Reply #18 on: April 21, 2006, 03:48:08 PM »

WB2WIK:
>>Probably the "boonies" situation, I'd guess.

Your right on that one...  I am net control for the Miami-Dade Areas races VHF simplex net every WED @ 7:pm and my station does indeed have good ears..  

I monitored the MURS channels with my 746 pro, My radio cannot TX out of band, But can receive.. I am quite certain my station can "hear" well..

Theres not much VHF activity here, heck on 2M VHF SSB there only activy I hear is during contests..

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KI4CYB
Member

Posts: 47




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« Reply #19 on: April 21, 2006, 03:56:18 PM »

QTH is actually West Kendall (Still within Miami-DADE) But all the way West near everglades...
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WB4QNG
Member

Posts: 362




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« Reply #20 on: April 21, 2006, 05:03:35 PM »

There isn't much at all on the FRS around here in Louisville, Ky.  Every once in a while you might find some kids using them. Not very often
Terry
WB4QNG
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KI4CYB
Member

Posts: 47




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« Reply #21 on: April 22, 2006, 07:06:26 AM »

Actually there allot of FRS/GRMS activity around here...  I guess its easier for people to buy those cheapy handhelds that almost all the stores sell...

But there's no activity on the 3 151mhz channels and some business activity on the 2 154Mhz channels on MURS...  I guess this is due to 2M MURS radios not for sale locally...

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